Method and devices for interfacing a plurality of mobile elements with a computer system in real time

ABSTRACT

The subject of the invention is in particular the real-time interfacing of a plurality of mobile elements with a computing system. After having selected at least one location module integrated into a mobile element, the at least one location module is activated sequentially. At least one signal is then received from the at least one activated location module and at least one item of information relating to the position of the mobile element including the at least one activated location module is calculated in real time on the basis of the at least one signal received. A single location module may be activated at a given instant.

The present invention relates to interfaces between a user and acomputer system, in particular in the field of games, and moreparticularly to a method and devices for interfacing a plurality ofmobile elements with a computer system.

In many situations, it may be necessary for a computer system to detectthe position and/or orientation of mobile elements to allow the latterto react accordingly. Thus, for example, in a chess game allowing a userto play against a virtual player simulated by the computer system, theapplication implemented on the computer system must know the position ofall the pieces on the chess board, in particular those moved by theuser, in order to calculate its move.

There are solutions for detecting the position and/or orientation ofreal objects on a game board, making it possible to use these objects asan interface for a computer system.

Thus, for example, touch screens of the resistive type can be used as agame board in order to detect the position of an object such as a penwhen sufficient pressure is applied. However, this type of screengenerally only supports a single contact and requires constant pressureby the user to determine the position. In other words, it is notpossible to detect the position of the pen if the pressure exerted bythe latter is removed.

It is also possible to use touch screens of the capacitive type, basedon the principle of current leakage through a conductive body. However,only conductive objects connected to earth allow for the detection oftheir position. Thus, for example, the positions of plastic or woodenobjects cannot be determined using such screens.

Moreover, in general, solutions based on touch screens or touch filmonly support a limited number of simultaneous or quasi-simultaneouscontacts and do not allow for the determination of a large number ofobjects.

Other solutions implement technologies based on infrared, in particularin the form of tables. Thus, for example, products known under the namesSurface (Surface is a trademark of Microsoft), mTouch (mTouch is atrademark of Merel Technologies) and Entertaible (Entertaible is atrademark of Philips) use infrared cameras arranged within the thicknessof the table. However, the required thickness of these tables makes thembulky and less mobile and gives them a certain rigidity. In addition,their price does not really allow for family use.

Finally, these solutions do not allow for the detection of the altitude,in relation to a predetermined reference, of mobile elements themovements and/or orientations of which are detected.

The invention makes it possible to solve at least one of the problemsdescribed above.

The object of the invention is thus a method for interfacing in realtime a plurality of mobile elements with a computer system, the methodcomprising the following steps:

-   -   transmission of an activation signal to at least one        localisation module incorporated in at least one mobile element        of said plurality of mobile elements;    -   sequential activation of said at least one localisation module,        said activation comprising a switching step to excite an element        radiating from said at least one localisation module;    -   reception of at least one signal from said at least one        activated localisation module;    -   calculation, on the basis of said at least one received signal,        of at least one item of information on the position of said        mobile element comprising said at least one activated        localisation module,        a single localisation module being able to be activated at a        given instant.

The process according to the invention thus enables a computer system todetermine simply, efficiently, and in real time the position of a largenumber of mobile elements which can be used to interact with thecomputer system.

According to a particular embodiment, said activation signal comprisesan item of data making it possible to identify a localisation module inorder to selectively activate a single localisation module. Theactivation sequence is thus determined by the computer system and thelogic unit of the localisation modules is simple in that it essentiallyconsists of comparing a received identifier with a predeterminedidentifier.

According to another particular embodiment, said activation signal is acommon activation signal for common control of the activation of aplurality of localisation modules. According to this embodiment, theactivation sequence is determined by the logic unit of the localisationmodules in combination with the computer system or not. According tothis embodiment, the computer system does not need prior knowledge ofthe localisation modules.

Still according to a particular embodiment, the method further comprisesa step to calculate a time delay value for each localisation module ofsaid plurality of localisation modules, said time delay valuerepresenting a time interval between the reception of an activationsignal and the activation of the module localisation. The activationsequence of the localisation modules is thus defined by time delayvalues associated therewith.

Each time delay value is, for example, determined according to an itemof identification data of the localisation module.

The time delay values can be dynamically determined thereby making itpossible to interface new mobile elements and/or remove mobile elementsfrom the interface without the need to reconfigure it. Such dynamicdetermination can in particular be based on the use of a time-divisionmultiple access algorithm.

Said common activation signal can be induced by a signal usedindependently of said process. This can involve, for example, a signalinduced by a synchronization frame of a screen being used. It istherefore not necessary in this case to generate a specific signal.

According to a particular embodiment, the method further comprises astep to calculate at least one item of information on the orientation ofsaid mobile element, said mobile element comprising at least twolocalisation modules.

Still according to a particular embodiment, the method further comprisesa step to transmit at least one item of data from said at least onelocalisation module to said computer system. Said at least one item ofdata can in particular be representative of an identifier of said atleast one localisation module. In this case, it allow, the computersystem to associate a position with a localisation module. It can alsobe representative of a state of the localisation module or a functionassociated therewith.

Still according to a particular embodiment, the method further comprisesa step to check the validity of said at least one localisation module,said step of sequential activation of said at least one localisationmodule being performed in response to said validity check step. Thus,only the positions and/or orientations of the mobile elements playing anactive role in interfacing with the computer system are determined

The method preferably further comprises a step of assigning a state ofvalidity or invalidity to said at least one localisation module, saidstate of validity or invalidity being determined according to said atleast one item of position information.

Still according to a particular embodiment, said step to receive atleast one signal comprises a step to sequentially select a plurality ofreceivers, said at least one signal being received by at least onereceiver selected from said plurality of receivers. It is thus possibleto determine the position of a localisation module according to thecharacteristics of the signals received and the receivers selected.

A further object of the invention is a mobile element for a device tointerface a plurality of mobile elements with a computer system, saidmobile element comprising at least one localisation module, saidlocalisation module comprising the following means:

-   -   means for emitting a signal making it possible to calculate the        position of said localisation module;    -   means for generating an excitation signal of said means for        emitting a signal;    -   switching means for controlling the transmission of said        excitation signal to said means for emitting a signal, and,    -   means for receiving an activation signal and, according to at        least one item of information of said activation signal,        activating said switching means to enable the emission of a        signal which can be used to calculate the position of said        localisation module.

The mobile element according to the invention thus enables a computersystem to determine simply, efficiently and in real time the position ofa large number of mobile elements which can be used to interact with thecomputer system.

According to a particular embodiment, said means for receiving anactivation signal comprise means for calculating a time delay value,said time delay value representing a time interval between the receptionof an activation signal and the activation of said switching means.

The activation sequence of the localisation modules is thus defined bythe time delay values associated therewith.

Still according to a particular embodiment, said at least onelocalisation module comprises at least one solenoid, excitable byinduction, for supplying electric power to components of said at leastone localisation module.

A further object of the invention is a device to interface a pluralityof mobile elements with a computer system, the device comprising meanssuitable for implementing each of the steps of the method describedabove. The advantages of such a device are similar to those mentionedabove.

Other advantages, purposes and features of the present invention willbecome apparent from the following detailed description, given by way ofa non-limitative example, in the light of the attached drawings inwhich:

FIG. 1 shows diagrammatically an example of an architecture implementingthe invention;

FIG. 2 shows an example of a detection surface and associated logic unitin accordance with the invention, according to a first embodiment;

FIG. 3 shows diagrammatically the physical principle of inductivecoupling between a solenoid and a conductive loop of a detectionsurface;

FIG. 4 shows diagrammatically an interpolation mechanism making itpossible to calculate the position of a solenoid placed on a detectionsurface, along a given axis, on the basis of measurements obtained by asystem such as that described with reference to FIG. 2

FIGS. 5 and 6 show an example of a detection surface and associatedlogic unit in accordance with the invention, according to second andthird embodiments, respectively;

FIG. 7 shows diagrammatically logic blocks of a localisation module of amobile element the position and/or orientation of which can bedetermined on the basis of a system such as those shown in FIGS. 2, 5and 6;

FIG. 8 shows an example of electronic implementation of the logicdiagram described with reference to FIG. 7 relating to a localisationmodule of a mobile element the position and/or orientation of which canbe determined;

FIG. 9, comprising FIGS. 9 a and 9 b, shows diagrammatically twoexamples of mobile elements the position of which can be determined andthe position and orientation of which can be determined, respectively;

FIGS. 10 and 11 show examples of algorithms which can be used tosequentially activate a set of localisation modules and calculate thepositions and/or orientations of the corresponding mobile elements;

FIG. 12 shows an example of a timing chart for the activation oflocalisation modules as a function of a common activation signal;

FIG. 13, comprising FIGS. 13 a and 13 b shows a third example of analgorithm which can be used to sequentially activate a set oflocalisation modules by means of a common activation signal, and,

FIG. 14 shows a timing chart for a system for the dynamic activation oflocalisation modules.

The invention relates generally to determining the position (abscissa,ordinate and/or altitude) and/or orientation (heading, pitch and/orroll) of mobile elements or pieces arranged on a surface and usedtogether. For these purposes, the invention implements a surface for thedetection of mobile elements, mobile elements each provided with atleast one localisation module and an activation module making itpossible to determine the position and, preferably, the orientation, ofeach mobile element, sequentially. The position can be a two-dimensionalposition, in one plane, or a three-dimensional position comprising analtitude (or elevation). The invention thus relates to a novel interfacebetween a user and a computer system associated with the position andorientation of several mobile elements. The detection surface can becombined with a screen to provide, for example, elements of decor orinformation.

By way of illustration, three-dimensional positions of mobile elementscan be captured by an electromagnetic field. For this purpose, a surfacefor the detection of the positions of mobile elements, consisting of anelectromagnetic capture mesh of the line/column type is used. It iscombined with an electronic module capable of calculating, bydemultiplexing, the position of a localisation module emitting anelectromagnetic field.

Each localisation module is therefore selected sequentially, for exampleaccording to an identifier specific thereto, so that it emits anelectromagnetic field. For this purpose, each localisation modulecomprises an activation mechanism such that, when activated, it emits anelectromagnetic field which can be captured by the detection surface.

A position detection control module is associated with the detectionsurface in order to sequentially activate electromagnetic emissions ofthe localisation modules via a control signal or to control suchsequential activation. The control signal between this module and thelocalisation modules can be transmitted via a wired connection orpreferably via wireless connections, for example an HF (High Frequency)radio signal or a signal complying with Wi-Fi, ZigBee, or Bluetoothstandards (Wi-Fi, Bluetooth and ZigBee are trademarks).

The surface for the detection of the positions is, for example, a PCB(Printed Circuit Board) type card for electromagnetic reception,flexible or rigid. It can be combined with a screen, also flexible orrigid, tactile or not, for example an LCD (Liquid Crystal Display) orOLED (Organic Light-Emitting Diode) type screen, making it possible tomove the mobile elements on an interactive visual surface. The detectionsurface can also be combined with a magnetized surface, making itpossible to move the mobile elements on an inclined plane, vertical orinverted (upside down) or subjected to shocks, without altering theposition detection.

FIG. 1 shows diagrammatically an example of an architecture 100implementing the invention.

The architecture 100 here comprises a board 105, for example a gameboard, on which mobile elements 110 are arranged, enabling a user tointeract with a computer system combined with the board by moving themobile elements 110. Although only five mobile elements are shown here,it is possible to use several tens or even several hundreds. The board105 defines the position and/or orientation detection zone of the mobileelements used.

The board 105 here comprises a detection surface 115 coupled to a screen120 and a magnetized surface 125 (the detection surface 115, the screen120, and the magnetized surface 125 are here substantially parallel). Italso comprises a hardware module 130 (or central processing system) todetect the position and, if necessary, the orientation of the mobileelements 110 as well as to implement one or more applications with whichthe user interacts. The hardware module 130 is in particular responsiblefor managing the detections of the positions and/or orientations of themobile elements, i.e. identifying the localisation modules one afteranother, activating them so that they emit, each in turn, anelectromagnetic field, and evaluating their positions.

The hardware module 130 is preferably inserted into a casing with theother elements of the board 105. Alternatively, it can be a remotemodule incorporated, for example, in a computer or a game console. Itcan be electrically powered by rechargeable battery or via a mainsadapter and presents a set of standard connections 135, for example anelectrical socket for a mains adapter, USB, Ethernet, VGA (VideoGraphics Array) and/or HDMI (High Definition Multimedia) ports, asappropriate, in particular if a screen is combined with the detectionzone. It also comprises, preferably, a wireless communication module,for example a WiFi or Bluetooth type wireless communication modulemaking it possible to interact with another computer system and/or toaccess data via a communication network.

The hardware module 130 typically comprises a calculation module and acontrol module for position detection and capture, as detailed below.The calculation module is fitted here with a central processing unit(CPU), a graphics processing unit (GPU), memory components (RandomAccess Memory (RAM), Read Only Memory (ROM), and/or Flash type memory)to store the programs and variables needed for the implementation of theinvention as well as an audio processing module in the form, forexample, of a chipset.

The control module for position detection and capture sequentiallyactivates, preferably by radio, each localisation module the position ofwhich is to be determined or controls such a sequential activation.After activation, each localisation module here emits an electromagneticfield captured by the detection surface. The latter then transmits tothe module for position detection and capture, information making itpossible to calculate the position of a localisation module, for exampleof the (x, y, z) type. As described below, when several localisationmodules are combined within a single mobile element, it is possible, onthe basis of the positions of these localisation modules, to determineorientation parameters of the mobile element, for example in the form ofangles. The positions and/or orientation of all the mobile elements theposition and/or orientation of which are to be determined are thentransmitted to the calculation module, which uses them to manage theinteractivity with the application in question.

FIG. 2 shows an example of a detection surface and associated logic unitaccording to a first embodiment.

The detection surface 115 is here made up of a mesh in the form of linesand columns forming a conductive grid. The latter comprises a set ofconductive loops along two orthogonal axes. Each loop is a discretesensor making it possible to measure the intensity of the current orvoltage induced by a radiating element, typically a solenoid belongingto a mobile element the position and/or orientation of which are to becalculated, which is positioned on the detection surface.

By way of illustration, it is assumed here that a solenoid is placed atposition 200, i.e. at the intersection of loops 205 and 210 of which oneend is connected to earth and the other end is connected to theelectronic components used to calculate a position. When the solenoidlocated at position 200 is supplied with power, it generates aninductive current in loops 205 and 210 which can be analysed andcompared with the current induced in the other loops. It is thuspossible, by inductive coupling between the solenoid and the grid and bymeasuring the induced current, to determine the position of thesolenoid.

Multiplexers 215 and 220 are connected to each loop of each of the twoaxes of the grid, i.e. in this case to each of the vertical andhorizontal loops, respectively. The outputs from multiplexers 215 and220 are connected to automatic gain controllers (AGC) 225 and 230,respectively, of the control module for position detection and capture,referenced here as 130-1, of the hardware module 130. The output signalsfrom the automatic gain controllers 225 and 230 are first of alldemodulated in the demodulators 235 and 240, respectively. Demodulationproduces a direct current (DC) signal proportional to the original sinewave supplemented by multiple alternating current (AC) components of thefixed frequency emitted by the solenoid.

According to a commonly-used configuration, the calculation module,referenced here as 130-2, of the hardware module 130 controls themultiplexers 215 and 220 in order to sequentially activate the loops,i.e. to activate a loop n+1 after a loop n. When the last loop isreached, the processor initiates a new cycle and controls the activationof the first loop.

A low-pass filter is advantageously used in each demodulator 235 and 240to suppress the unwanted harmonics of the demodulated signal as well asthe electromagnetic background noise. This filtering makes it possibleto refine the measurements of the signals originating from the automaticgain controllers 225 and 230, after demodulation, which are thendigitized in analog/digital converters (ADC) 245 and 250, respectively.

The digital values obtained are transmitted to the central processingunit (CPU) 255 of the calculation module 130-2 to be stored. As shown,the central processing unit 255 controls the demodulators 235 and 240.

After the values have been stored, the central processing unitincrements the address of the multiplexers in order to proceed todigitisation of the signals originating from the following loops. When alast loop is reached, the central processing unit reinitializes theaddress of the multiplexer corresponding to the value of the first loopof the axis in question.

At the end of a cycle, the central processing unit has stored, for eachaxis, as many digital values as there are adjacent loops near theposition of the solenoid. On the basis of these values, the centralprocessing unit calculates the position of the solenoid by interpolationas described below.

It is noted here that the loops can be earthed by metal stripspositioned between the different loops in order to protect them againstelectromagnetic interference. An alternative consists of placing auniform earth plane under the conductive grid.

In addition, the control module for position detection and capture 130-1here comprises a radio emitter 260, controlled by the central processingunit 255 of the calculation module 130-2, making it possible to activatea localisation module of a mobile element. By way of illustration, thecentral processing unit 255 transmits to the radio emitter 260 anidentifier of a localisation module to be activated. This identifier isencoded and then transmitted in the form of a digital or analog radiosignal. Each localisation module receiving this signal can then comparethe identifier received with its own identifier and activate itself ifthe identifiers are identical.

Thus, in order to estimate the position of a set of localisationmodules, it is necessary to perform a cycle on each localisation moduleand, for each of these cycles, according to the embodiment describedhere, a cycle on each set of loops.

Several detection surfaces can be combined with each other, theresulting surface area of the detection surface being the sum of thesurface areas of the detection surfaces combined. For these purposes,one detection surface is considered to be the master, the others beingconsidered slaves. The sequential activation of the mobile elements ismanaged by the master detection surface, which receives, preferably, thepositions calculated by the hardware modules associated with each slavedetection surface and consolidates them by producing a table containingthe coordinates and angles of freedom of the localisation modules.

FIG. 3 shows diagrammatically the physical principle of inductivecoupling between a solenoid and a conductive loop of a detectionsurface.

According to the invention, each mobile element the position and/ororientation of which are to be calculated comprises at least onesolenoid the axis of which is preferably directed towards the detectionsurface.

An alternating current passes through the solenoid 300 and it emits anelectromagnetic field which is propagated towards the detection surface,in particular, in this example, towards the loop 210. The loop 210,receiving an electromagnetic field originating from the solenoid 300, iscoupled with the solenoid 300. It is then possible to measure analternating current signal at the terminals of this loop, referenced305.

The coupling between the solenoid 300 and the loop 210 can be expressedin the form of the following equation,

$R = {\frac{k}{D^{2}}E}$

wherein

E denotes the voltage at the terminals of the solenoid 300, R denotesthe voltage of the signal received at the terminals 305 of the receivingloop 210, D is the distance between the solenoid 300 and the receivingloop 210 and k is a constant associated with factors intrinsic to thesystem comprising the solenoid and the receiving loop, in particular thenumber of turns of the solenoid and the size of the loop.

FIG. 4 shows diagrammatically an interpolation mechanism making itpossible to calculate the position of a solenoid placed on a detectionsurface, along a given axis, on the basis of the measurements obtainedby a system such as that described with reference to FIG. 2.

It is assumed here that the solenoid is located close to vertical loopsB3, B4 and B5, positioned at abscissa X3, X4 and X5, the voltagesmeasured at the terminals of these loops being denoted V3, V4 and V5,respectively. The solenoid is located here in a position, on the x-axis,denoted XS.

Coordinates X3, X4 and X5 can be obtained by the central processing uniton the basis of an identifier of the corresponding loop (these valuesare predefined according to the routing configuration of the detectionsurface and, preferably, stored in a non-volatile memory).

The portion of curve 400 shown in FIG. 4 shows the variation in voltagefor the solenoid position XS according to the positions of the loopscoupled with the solenoid, extrapolated from the values measured by theloops B3, B4 and B5. It can be likened to a second degree function ofthe parabolic type. This local approximation corresponds, in practice,to the phenomenon of electromagnetic coupling between a solenoid andloops of a conductive grid.

The following relationships illustrate this property.

V3=a(X3−XS)² +b

V4=a(X4−XS) ² +b

V5=a(X5−XS) ² +b

where a and b are constants, a being a constant less than zero (a<0).

Moreover, given the assumption of a second degree function, therelationships between the abscissa X3, X4 and X5 can be expressed in thefollowing form:

X4−X3=X5−X4=ΔX

X5−X3=2ΔX

X representing the distance between the abscissa X3 and X4 and betweenthe abscissa X4 and X5).

Thus, it is possible to interpolate the position of the solenoidaccording to the following formula:

${XS} = {{X\; 3} + {\frac{\Delta \; X}{2}\frac{{3V\; 3} - {4V\; 4} + {V\; 5}}{{V\; 3} - {2V\; 4} + {V\; 5}}}}$

It is also possible, according to the same logic, to determine theposition of the solenoid along the y-axis.

In addition, the distance between the solenoid and the loop (i.e. thealtitude of the solenoid relative to the detection surface) can bedefined by the following relationship:

$D = \sqrt{\frac{k}{R}E}$

The distance D is therefore a function of the value R representing thevoltage at the terminals of the relative loops of the detection surface.It can be extrapolated from the measurements made. It is noted that theaccuracy of the distance calculation is in particular linked to thestability of the signal E emitted by the solenoid, the value of whichshould be as constant as possible over time, which requires a stabilizedpower supply in the localisation module, which should not drop as thebattery discharges. This can be ensured by a voltage regulator in thelocalisation module.

FIG. 5 shows an example of a detection surface and associated logic unitaccording to a second embodiment.

An essential difference between the detection surface and associatedlogic unit shown in FIGS. 2 and 5 lies in the use of additionalmultiplexers and differential amplifiers.

Like the detection surface 115 described above, the detection surface115′ here is made up of a mesh in the form of lines and columnsconstituting a conductive grid comprising a set of loops along twoorthogonal axes. Similarly, each loop is a discrete sensor making itpossible to measure the intensity of the current or voltage induced by asolenoid (belonging to a mobile element the position and/or orientationof which are to be detected), which is positioned on the detectionsurface.

Two multiplexers are linked here with each set (vertical and horizontal)of loops. Thus, for each of the two dimensions of the grid, a firstmultiplexer is alternately connected one loop out of every two while asecond multiplexer is connected to the remaining loops. Multiplexer215′-1 is connected here to the odd vertical loops while multiplexer215′-2 is connected to the even vertical loops. Similarly, multiplexer220′-1 is connected here to the odd horizontal loops while multiplexer220′-2 is connected to the even horizontal loops.

The outputs from multiplexers 215′-1 and 215′-2 connected to thevertical loops are connected to a differential amplifier 500 while theoutputs of multiplexers 220′-1 and 220′-2 connected to the horizontalloops are connected to a differential amplifier 505.

The multiplexers and differential amplifiers therefore produce, for eachaxis of the detection surface grid, an immediate comparison between thesignals received by two adjacent loops. In other words, the outputsignal from each differential amplifier is a differential signal.

Processing similar to that described with reference to FIG. 2 is thenapplied to the differential signals. However, the filtering here isadaptive filtering (and not low-pass filtering) in order to suppress thecommon noise and the noise associated with demodulation and, thus,increase the signal-to-noise ratio. This embodiment allows for greateramplification and, consequently, better accuracy in the calculation ofpositions. The central unit of the calculation module controls theadaptive filter so that it is preferably reset to zero after the end ofeach cycle of measurements.

The output from each differential amplifier 500 and 505 is connected toan automatic gain controller (AGC) 225′ and 230′ respectively of thecontrol module for position detection and capture, referenced here130′-1. The output signals from the automatic gain controllers 225 and230 are first of all demodulated in demodulators 235′ and 240′respectively in order to obtain a direct current signal proportional tothe original sine wave supplemented by multiple alternating currentcomponents of the fixed frequency emitted by the solenoid.

Again, the calculation module, referenced here 130′-2, controlsmultiplexers 215′-1, 215′-2, 220′-1 and 220′-2 in order to sequentiallyactivate the loops, i.e. to activate a loop n+1 after a loop n. When thelast loop is reached, the processor initiates a new cycle and controlsthe activation of the first loop.

As indicated previously, an adaptive filter is advantageously used ineach demodulator 235′ and 240′ in order to suppress undesirableharmonics of the demodulated signal and the background electromagneticnoise. This filtering makes it possible to refine the measurements ofsignals originating from the automatic gain controllers 225′ and 230′,after demodulation, which are then digitized in the analog/digitalconverters 245′ and 250′, respectively.

The digital values obtained are transmitted to the central processingunit 255′ of the calculation module 130′-2 to be stored. As shown, thecentral processing unit 255′ controls the demodulators 235′ and 240′.

Again, after the values have been stored, the central processing unitincrements the address of the multiplexers in order to proceed todigitisation of the signals originating from the following loops. When alast loop is reached, the central processing unit reinitializes theaddress of the multiplexer corresponding to the value of the first loopof the axis in question.

At the end of a cycle, the central processing unit has stored, for eachaxis, as many digital values as there are adjacent loops near theposition of the solenoid. On the basis of these values, the centralprocessing unit calculates the position of the solenoid by interpolationas described above.

The loops can also be earthed here by metal strips positioned betweenthe various loops in order to protect them from electromagneticinterference, an alternative consisting of placing a uniform earth planeunder the conductive grid.

Like the control module for position detection and capture 130-1described with reference to FIG. 2, the control module for positiondetection and capture 130′-1 here comprises a radio emitter 260′,controlled by the central processing unit 255′ of the calculation module130′-2, making it possible to activate a localisation module.

FIG. 6 shows an example of a detection surface and associated logic unitaccording to a third embodiment.

This embodiment is based on that described with reference to FIG. 2. Italso comprises two fixed-gain amplifiers, two demodulation chains withlow-pass filtering and analog/digital conversion per axis of theconductive grid. This embodiment allows for a precise calculation of thealtitude of the mobile elements located above the detection board.

It is noted here that the altitude calculation requires the use ofabsolute position data (and not relative as is possible for positionsalong the x-axes and y-axes).

For this purpose, a second position capture chain is implemented wherethe automatic gain controller is replaced by a constant gain amplifier.The loss of accuracy resulting from the omission of the automatic gaincontroller is replaced by the ability of the constant gain amplifier toprovide absolute measurements.

The detection surface 115″ is again made up of a mesh in the form oflines and columns constituting a conductive grid comprising a set ofloops along two orthogonal axes, each loop forming a discrete sensormaking it possible to measure the intensity of the current or voltageinduced by a solenoid (belonging to a mobile element the position and/ororientation of which are to be detected), which is positioned on thedetection surface.

Multiplexers 215″ and 220″ are connected to each loop of each of the twoaxes of the grid, i.e. here to each of the vertical and horizontalloops, respectively. The outputs of multiplexers 215 and 220 areconnected to the automatic gain controllers (AGC) 225″ and 230″ as wellas to the fixed-gain amplifiers 600 and 605, respectively, of thecontrol module for position detection and capture, referenced here130″-1.

The output signals of the automatic gain controllers 225″ and 230″ arefirst of all demodulated in the demodulators 235″ and 240″,respectively. The demodulation produces a direct current signalproportional to the original sine wave supplemented by multiplealternating current components of the fixed frequency emitted by thesolenoid.

Similarly, the output signals of fixed-gain amplifiers 600 and 605 arefirst demodulated in demodulators 610 and 615, respectively.

Again, the calculation module, here referenced 130″-2 controlsmultiplexers 215″ and 220″ in order to sequentially activate the loops,i.e. to activate a loop n+1 after a loop n. When the final loop isreached, the processor initiates a new cycle and controls the activationof the first loop.

A low-pass filter is advantageously implemented in each demodulator235″, 240″, 610 and 615 in order to suppress the unwanted harmonics ofthe demodulated signal as well as the background electromagnetic noise.This filtering makes it possible in particular to refine themeasurements of the signals originating from the automatic gaincontrollers 225″ and 230″, after demodulation.

The output signals of the demodulators 235″, 240″, 610 and 615 are thendigitized in the analog/digital converters (ADC) 245″, 250″, 620 and625, respectively.

The digital values obtained are transmitted to the central processingunit 255″ of the calculation module 130-2″ to be stored. As shown, thecentral processing unit 255″ controls the demodulators 235″, 240″, 610and 615.

After the values have been stored, the CPU increments the address of themultiplexers in order to proceed to digitisation of the signalsoriginating from the following loops. When a last loop is reached, thecentral processing unit reinitializes the address of the multiplexercorresponding to the value of the first loop of the axis in question.

At the end of a cycle, the central processing unit has stored, for eachaxis, as many numerical values as there are adjacent loops near theposition of the solenoid. On the basis of these values, the centralprocessing unit calculates the position of the solenoid by interpolationas described above.

It is noted here that the loops can be earthed by metal stripspositioned between the different loops in order to protect them againstelectromagnetic interference. An alternative consists of placing auniform earth plane under the conductive grid.

In addition, the control module for position detection and capture130″-1 here comprises a radio transmitter 260″, controlled by thecentral processing unit 255″ of the calculation module 130″-2, making itpossible to activate a localisation module.

The mobile elements the position and/or orientation of which are to bedetermined contain at least one localisation module incorporating anactivation receiver, preferably wireless, for example an HF, Wi-Fi,ZigBee or Bluetooth radio communication module, making it possible toreceive a command to activate their electromagnetic emissions. Eachlocalisation module is capable of determining whether the activationcommand received, emitted by a control module for position detection andcapture, is addressed to it or not. An item of identificationinformation on the localisation module to be activated can betransmitted in analog or digital form.

FIG. 7 shows diagrammatically the logic blocks of a localisation modulefor a mobile element the position and/or orientation of which can bedetermined on the basis of a system such as that described above.

Such a mobile element is, preferably, independent as regards both itselectric power supply and the reception of electromagnetic emissioncommand signals.

The localisation module 700 thus comprises an electric power supplymodule 705 supplying a voltage for all the components of thelocalisation module as well as a command reception and detection module710, which receives and demodulates a signal, for example an HF signal,emitted by an external control module for position detection andcapture, in order to determine whether the signal received is intendedto activate the localisation module. As described above, such detectioncan be performed by comparing an identifier received with a previouslystored identifier.

The localisation module 700 also comprises a switch 715, controlled bythe command reception and detection module 710, as well as a selectiveamplifier 720 controlled by the switch 715. Finally, the localisationmodule 700 comprises a local oscillator 725 generating a frequency,preferably fixed, stable, and of the square type and a solenoid 730.

The selective amplifier 720 generates, depending on the position of theswitch 715 and on the basis of the signal originating from the localoscillator 725, a sine wave voltage at the terminals of the solenoid730, allowing the solenoid 730 to generate sufficient radiation poweralmost instantaneously (i.e. in real time). The almost instantaneousoscillation turn-on and cut-off time of the selective amplifier areobtained by the pairing formed by the local oscillator 725 and theselective amplifier 720.

For this purpose, the local oscillator 725 and the selective amplifier720 are, according to a first embodiment, always active when thelocalisation module is powered (they are not stopped as a function ofthe activation of the localisation module). The switch 715 is then usedto route the signal from the local oscillator 725 to the input to theselective amplifier 720 or not. Thus, when the local oscillator 725 isswitched to the selective amplifier 720, the selective amplifier 720reaches its specific oscillation frequency in a very short time,typically a few microseconds (a standard oscillator of the RLC type inquestion requires a turn-on time of a few milliseconds, incompatiblewith real time). Cut-off of the selective amplifier 720, consisting indisconnecting the local oscillator 725 from the selective amplifier 720is, for the same reasons, almost instantaneous (of the order of amicrosecond).

According to another embodiment, the local oscillator 725 is alwaysactive when the localisation module is powered (it is not stopped as afunction of the activation of the localisation module), while theselective amplifier 720 is only powered when the localisation module isactivated. The purpose of the switch 715 is then to control the electricpower supply for the selective amplifier 720. The selective amplifierturn-on and cut-off time are similar to those of the first embodiment.

Several types of electric power supply can be used for the localisationmodule. The power supply can be obtained from a rechargeable battery anda standard control circuit. It can also be obtained from a battery and avoltage regulator making it possible to obtain a constant voltagethroughout a range of use of the battery. This solution is particularlyadvantageous when the system has to calculate the altitude of mobileelements implemented.

Power can also be supplied indirectly by remote supply. According tothis embodiment, a layer of dedicated radiating solenoids is placedunder the detection surface. A sine wave signal passes through thesesolenoids and the power emitted by each solenoid is sufficient for aremote power supply to the localisation modules positioned above it. Thelocalisation modules are also equipped with a solenoid for reception, byinduction, of the signal emitted by the solenoids present beneath thedetection surface.

The remote power supply can also be coupled with the use of ahigh-capacity capacitor, which is charged from the solenoid of thelocalisation module. The capacitor is then used as a voltage source tosupply power to the other modules. Alternatively, the remote powersupply can be coupled with the use of a battery present in the mobileelement, for example a lithium battery. The solenoid of the localisationmodule then constantly recharges this battery as soon as an inducedcurrent passes through it. A charge/discharge protection circuit isadvantageously associated with the battery so that it remains within itsrange of acceptable voltages. As previously indicated, if the altitudeof mobile elements has to be assessed, the voltage source is preferablyregulated so that the power supply voltage is constant during use ofthis voltage source, i.e. during estimation of the position and/ororientation of the mobile element.

The mobile elements located on a detection surface and used together canuse different types of power supply.

Furthermore, when a mobile element comprises more than one localisationmodule, certain components, in particular the electric power supply, canbe common to some or all of the localisation modules.

FIG. 8 shows an example of electronic implementation of the logic unitconfiguration described with reference to FIG. 7 relating to alocalisation module of a mobile element the position and/or orientationof which can be determined

The electronic configuration shown in FIG. 8 relates to an analog modewith transmission of N carriers by the control module for positiondetection and capture, N representing the maximum number of localisationmodules the positions of which can be calculated by the system.

The purpose of the command reception and detection module 710 here is todetect the frequency of the carrier associated with the localisationmodule in question. It comprises, in this example of implementation, areceiving antenna 800 and an LC network, comprising a capacitor 802 andan inductor 804 tuned to the emission frequency of the control modulefor position detection and capture. It also comprises a diode 806 tosuppress the negative component of the signal and a low-pass RC filtercomprising a resistor 808 and a capacitor 810 to suppress the carrier.If the carrier is present, a signal is present at the output from thefilter, while, if the carrier does not correspond to the localisationmodule in question, the signal is zero at the output from the filter.The command reception and detection module 710 also comprises aswitching transistor 812, controlling the switch 715 via a resistor 814which makes it possible to activate the selective amplifier 720. Theswitching transistor 812 is here connected to the RC circuit via aresistor 816.

Such an implementation concerns reception of an amplitude-modulatedactivation signal. However, other modes such as frequency-modulatedreception or phase-modulated reception can be implemented.

The switch used is, for example, a Texas Instruments HC 4066 switch. Itcan be used to activate or deactivate the selective amplifier almostinstantaneously (real time). Activation is achieved when the switch isopen, i.e. when the selective amplifier is connected to the powersupply.

As described above, the local oscillator 725 generates, preferably, asquare signal the frequency of which is compatible with the conductiveloops of the detection surface (these loops being sized to receive aspecific frequency). Here, it comprises an oscillator 818, for example aLinear Technology Company LTC 1799 oscillator, coupled to a resistor820, here having a value of 4 kOhms, to define an oscillation frequencyof 250 KHz compatible with the frequency detected by the detectionsurface loops.

The selective amplifier 720 makes it possible to convert the squaresignal generated by local oscillator 725 into a sinusoidal signal. Italso ensures an optimum gain at the frequency of the local oscillatorand makes it possible to obtain the required intensity of the sine wavesignal passing through the solenoid 730 and therefore the optimumelectromagnetic radiation towards the detection surface used.

The selective amplifier is here implemented on the basis of a switchingtransistor 824, capacitors 826 and 828, and the network of resistors 830to 838. Capacitor 828 has, for example, a value of 33 μF, while resistor830 has a value of 2 kOhms, resistors 832, 834, 836, and 838 1 kOhm, andresistor 838 100 kOhms. Thus, the turn-on and cut-off times for theselective amplifier 720 are as short as possible.

The command reception and detection module 710 can be implementedaccording to variants other than that described above. In particular,apart from the analogue mode with transmission of N carriers by thecontrol module for position detection and capture, it is possible toimplement an analog mode using a single carrier containing a wantedsignal for the activation of a localisation module. According to thisvariant, a wanted signal the frequency of which is to be detected toactivate or a localisation module or not is available at the output fromthe low-pass RC filter. This signal can, for example, be filtered in aband-pass filter the resonant frequency of which is tuned to thespecific activation frequency of the localisation module in question.The output from this band-pass filter is then transmitted to a switchingtransistor which activates the analog switch allowing activation of theselective amplifier.

Alternatively, a digital mode with transmission of a single carriercontaining a wanted digital signal for the activation of a localisationmodule can be used. According to this variant, a wanted signal isavailable at the output from the low-pass RC filter. This signal istypically a square signal containing an item of digital informationencoded on several bits allowing activation of a plurality oflocalisation modules. Each localisation module is equipped with amicrocontroller, which decodes this signal and, as a function of theencoded value and a predetermined value, activates the analog switch andthus the selective amplifier.

Other communication protocols such as Wi-Fi, Bluetooth, or ZigBee can beused to transmit an activation command.

The pair formed by a local oscillator and a selective amplifier bringscertain advantages. In particular, since the local oscillator is alwaysactive, it is not necessary to activate and deactivate it. In addition,the selective amplifier used is the element which operates by switching(it is supplied with power or not according to the position of theanalog switch). Such an implementation thus authorizes a very shortactivation and deactivation time for the selective amplifier and makesit possible to optimize the switching times and thus the overall cycletime (a cycle corresponding to the activation/deactivation of the set oflocalisation modules).

However, it is possible to implement simpler variants of oscillatorswhich can replace the local oscillator and selective amplifier pair,typically an assembly known under the name of a Colpitts or Clapp typeassembly.

As described above, the localisation modules to be activated can beidentified in an analog or digital manner. The analog identification ofa localisation module can be performed by sending a dedicated frequency,according to several modes, in particular according to a carrierfrequency specific to each localisation module (this frequencyidentifies the localisation module which is activated). The on-boardelectronics thus react to the specific carrier corresponding thereto.Alternatively, a single carrier frequency can be used for all thelocalisation modules. This frequency modulates a wanted signal which isreceived by each localisation module. It is the value of the modulatedfrequency of this wanted signal which makes it possible to identify thelocalisation module to be detected. The activation frequencies for eachlocalisation module are, for example, defined in the factory duringassembly and are configured in the control module for position detectionand capture by means of the software.

The digital identification of a localisation module is performed bytransmitting a code, typically over several bits, in an activationmessage. This identification mechanism allows for greater flexibility ofuse since it allows programming (and thus modification) of theidentification of each localisation module.

FIG. 9, comprising FIGS. 9 a and 9 b, shows diagrammatically twoexamples of mobile elements the position of which can be determined andthe position and orientation of which can be determined, respectively.

The mobile element 110 shown in FIG. 9 a comprises a single localisationmodule 700. As shown, the radial axis of the solenoid is advantageouslyperpendicular to the plane of the detection surface so that theelectromagnetic radiation from the solenoid is propagated optimallytowards this surface.

The three-dimensional position of the mobile element 110, comprising asingle solenoid, can be calculated according to the invention, asdescribed above. In fact, on the basis of the calculated position of thesolenoid of the localisation module 700 and knowing the position of thismodule in the mobile element 110, it is possible to deduce therefrom theposition of the mobile element 110, i.e. the position of a referencepoint of this mobile element. When several mobile elements are presenton the detection surface, the position of each mobile element isdetermined sequentially.

The mobile element 110′ shown in FIG. 9 b comprises two independentlocalisation modules 700-1 and 700-2. Again, as shown, the radial axisof the solenoids is advantageously perpendicular to the plane of thedetection surface so that the electromagnetic radiation from thesolenoid is propagated optimally towards this surface.

Each solenoid 700-1 and 700-2 of the mobile element 110′ can beactivated independently of the other, in a sequential manner. Thus, itis possible to determine the position of the mobile element 110′ bydetermining the position of each solenoid of the localisation modules700-1 and 700-2 and knowing their position in the mobile element 110′.Similarly, it is possible to know the orientation of this mobile elementon the basis of the relative positions of the solenoids of localisationmodules 700-1 and 700-2 and their position in the mobile element 110′.It should be noted here that the use of the coordinates of the solenoidsof localisation modules 700-1 and 700-2 in the plane of the detectionsurface makes it possible to determine the orientation of the mobileelement 110′ in this plane, while the use of the altitude of thesolenoids of localisation modules 700-1 and 700-2 can be used tocalculate the pitch of the mobile element 110′.

It is noted here that mobile elements comprising a single solenoid andcomprising two solenoids can be used together on a detection surface,provided that the control module for position detection and capture iscapable of activating (directly or indirectly) each solenoidindependently of the others.

Capture of the orientation of mobile elements can thus be obtained byproviding each mobile element with at least two localisation modules(which are not to be aligned along a perpendicular to the detectionsurface) and defining a rule for identifying these localisation modules.

The roll of a mobile element can be determined by providing the latterwith two additional localisation modules (four localisation modules arethen used) and supplementing the identification rule for these modulesin order to associate identifiers for these four localisation moduleswith a mobile element.

On the basis of three-dimensional positions for four localisationmodules of a mobile element, it is possible to calculate its six degreesof freedom.

It is also possible, by associating three localisation modules with amobile element, forming an equilateral triangle, to calculateapproximately its six degrees of freedom.

The sequential activation of localisation modules, by a control modulefor position detection and capture, makes it possible to estimate theposition and/or orientation of a plurality of mobile elements providedwith such localisation modules.

When a localisation module receives an activation command dedicatedthereto, it triggers an electromagnetic emission. The detection system,knowing the identification of the emitting localisation module, can thenlink the items of calculated position information to the identifier ofthe localisation module.

The control module for position detection and capture is thusresponsible here for sequentially activating an electromagnetic emissionper localisation module, for recovering one by one a set of positionsand, knowing the links between the identifiers of the localisationmodules and identifiers of mobile elements, for calculatingorientations, if necessary, in order to associate positions and/ororientations with the identifiers of mobile elements. It thus constructsa table containing, for each mobile element, an identifier, an abscissa,an ordinate and, preferably, an altitude in a detection surfacereference as well as, if necessary, values for yaw, pitch and roll.

The sequential activation of the electromagnetic emission from thedetection modules permits the use of a single emission frequency for theset of moving elements managed by the system. Different activationalgorithms can be used by the control module for position detection andcapture. It is thus possible to activate all the localisation modulessystematically, to activate a subset of localisation modules, thissubset being, for example, defined by programming via the calculationmodule (such an implementation makes it possible in particular to reducethe overall duration of the complete activation sequence for thepieces), or activate localisation modules, depending on the context. Thelatter solution makes it possible, in particular, to manage the factthat certain mobile elements can leave the detection surface and thattheir positions and/or orientation no longer need to be calculated.However, a secondary loop preferably monitors their possiblereinstatement on the detection surface and the resulting need to capturetheir position and/or orientation again. This mode makes it possible tooptimize the overall duration of the activation sequence for the set ofmodules to be activated.

FIG. 10 shows a first example of an algorithm which can be used toactivate a set of localisation modules sequentially and calculate thepositions and/or orientations of the corresponding mobile elements.

A first step consists here of initialising a variable i, representing anindex on localisation modules, to the value zero (step 1000). In a nextstep (step 1005), the value of the variable i is compared with the valueof a constant M representing the number of localisation modulessupported by the system. Typically, the order of magnitude of theconstant M is a hundred. If the value of the variable i is greater thanor equal to that of the constant M, the variable i is reinitialized(step 1000).

If, on the other hand, the value of the variable i is less than that ofthe constant M, a test is performed to determine whether thelocalisation module having the index i is used (step 1010), i.e. whetherthe localisation module having the index i is valid. The validity of thelocalisation modules can be stored in a table which can be updated by anapplication using the interface formed by the mobile elements comprisingthese localisation modules and the system for locating these modules. Asshown by the use of dotted lines, this step is optional.

If the localisation module corresponding to the index i is valid, thatmodule is activated (step 1015). As described above, the activation ofthe localisation module having the index i consists, for example, ofemitting a signal the carrier of which has a frequency characterizing anidentifier of this localisation module.

When the localisation module having the index i is activated, it emitsan electromagnetic field enabling it to be located by measuring thevoltages induced in loops of the detection surface, as indicated above.

The control module for position detection and capture is then able tocalculate the position of the activated localisation module (step 1020).

These items of information are stored in order to be used by thecalculation module (step 1025). They can in particular be stored in atable of the positions of the localisation modules, on the basis ofwhich the positions and/or orientations of the mobile elementscomprising these localisation modules can be estimated.

The variable i is then incremented by one (step 030) and the previoussteps are repeated (steps 1005 to 1030) until the positions of all thelocalisation modules (or valid localisation modules) have beendetermined

Similarly, if the localisation module corresponding to the index i isnot valid (step 1010), the variable i is incremented by one (step 1030)and the previous steps are repeated (steps 1005-1030) until thepositions of all the localisation modules (or valid localisationmodules) have been determined.

The position and/or orientation of each mobile element are calculated onthe basis of the positions of the localisation modules. This calculationcan be performed when the positions of all the valid localisationmodules have been calculated or, mobile element by mobile element, whenthe positions of all the valid localisation modules belonging to thesame mobile element have been calculated.

It is noted here that the validity of localisation modules can be linkedin particular to the logic unit of the application using the interfaceformed by the mobile elements comprising these localisation modules andthe system for locating these modules. By way of illustration, in thecase of a game, invalid localisation modules can correspond to mobileelements representing pieces not in use in the game, for example pieceswhich have been taken during a game of chess or unused pieces in a givengame scenario.

FIG. 11 shows a second example of an algorithm which can be used toactivate a set of localisation modules sequentially and calculate thepositions and/or orientations of the corresponding mobile elements.

This algorithm makes it possible in particular to manage the fact thatcertain mobile elements can leave the zone of movement (i.e. here thedetection surface) and that the positions and/or orientations of thecorresponding mobile elements no longer need to be estimated. However, asecondary software loop monitors their possible reinstatement on thedetection surface and the resulting need to estimate their positionsand/or orientations again. This algorithm, in comparison with thealgorithm described with reference to FIG. 10, makes it possible toreduce the overall duration of the activation sequence for the set oflocalisation modules by dynamically managing their validity.

In this algorithm, the constant M corresponds to the maximum number oflocalisation modules supported by the system, the variable index icharacterizes the index of a localisation module, the table Pcorresponds to the table of positions of the localisation modules, tableV corresponds to the table of validity of the localisation modules, thevariable C is a global variable corresponding to the total number oflocalisation modules used, K is a predetermined constant correspondingto the maximum number of iterations of search for localisation modulesoutside the detection surface (a typical value for K is of the order ofaround ten), and A is a variable representing a countdown index ofiterations of search for localisation modules outside the detectionsurface for a global cycle.

The purpose of a first step is to initialize the variables i and C atzero (step 1100). In a next step, the value of the variable i iscompared with that of the constant M (step 1102). If the value of thevariable i is less than that of the constant M, the table of validity ofthe localisation modules is updated so that the localisation modulecorresponding to the index i is considered valid (step 1104). Thevariable i is then incremented by one (step 1106) and the new value ofthe variable i is compared with that of the constant M (step 1102).Steps 1102 to 1106 are used to initialize the table of validity of thelocalisation modules.

If, on the other hand, the value of the variable i is greater than orequal to that of the constant M, the variable i is reinitialized at zero(step 1108). In a next step, the value of the variable i is againcompared with that of the constant M (step 1110). If the value of thevariable i is less than that of the constant M, a test is performed todetermine whether the localisation module corresponding to the index iis valid (step 1112).

If the localisation module corresponding to the index i is valid, thatmodule is activated (step 1114) so that it emits an electromagneticfield enabling it to be located by measuring the voltages induced inloops of the detection surface.

The control module for position detection and capture is then able tocalculate the position and, if necessary, the orientation of theactivated localisation module (step 1116).

A test is then performed on the coordinates obtained for thelocalisation module (step 1118). If these coordinates are zero, thevalidity table for the localisation modules is updated so that thelocalisation module corresponding to the index i is considered invalid(step 1120). Otherwise, if these coordinates are non-zero, thesecoordinates are stored in order to be used by the calculation module(step 1122). They can, in particular, be stored in the table oflocalisation module positions, on the basis of which the positionsand/or orientations of the mobile elements comprising these localisationmodules can be estimated, as described above.

The variable i is then incremented by one (step 1124) and its value isagain compared with that of the constant M (step 1110).

Similarly, if the localisation module corresponding to the index i isnot valid (step 1112), the variable i is incremented by one (step 1124)and its value is again compared with that of the constant M (step 1110).

If the value of the variable i is greater than or equal to that of theconstant M (step 1110), the value of variable A is initialized at avalue of zero (step 1126). A test is then performed to compare the valueof the variable A with that of the constant K (step 1128). If the valueof the constant K is less than or equal to that of the variable A, thevalue of the variable i is reinitialized at zero (step 1108) and thesteps described above are repeated.

Otherwise, a test is performed to determine whether the localisationmodule corresponding to an index the value of which is equal to C isinvalid (step 1130).

If so, this module is activated (step 1132) so that it emits anelectromagnetic field making it possible for it to be located, forexample by measuring the voltages induced in the detection surfaceloops.

The control module for position detection and capture is then able tocalculate the position of the activated localisation module (step 1134).

A test is then performed on the coordinates obtained for thelocalisation module (step 1136). If these coordinates are zero, thevalidity table for the localisation modules is updated so that thelocalisation module corresponding to the index the value of which isequal to that of the variable C is considered invalid (step 1138).Otherwise, the validity table for the localisation modules is updatedsuch that the localisation module corresponding to the index the valueof which is equal to that of the variable C is considered valid (step1140).

The values of variables A and C are then incremented by one (step 1142).Similarly, if the localisation module corresponding to an index thevalue of which is equal to that of the variable C is not invalid (step1130), the values of variables A and C are then incremented by one (step1142).

A test is then performed to compare the value of the variable C withthat of the constant M (step 1144). If the value of variable C is lessthan that of the constant M, the values of the variable A and theconstant K are compared (step 1128) and the steps described above arerepeated.

If the value of the variable C is greater than or equal to that of theconstant M, the value of variable C is reinitialized at the value zero(step 1146). The values of variable A and constant K are then compared(step 1128) and the steps described above are repeated.

According to a third example of an algorithm which can be used tosequentially activate a set of localisation modules and calculate thepositions and/or orientations of the corresponding mobile elements, theactivation of all the localisation modules is initiated by a centralprocessing system (control module for position detection and capture)with a common activation signal, each localisation module independentlydetermining its activation as a function of the common activationsignal. The time delay values associated with each localisation module,i.e. here the delay between the detection of the common activationsignal (or one of its characteristics called activation “instruction” inthe rest of the description) and the activation of the localisationmodule, can be defined statically, for example by using an identifierstored in the localisation modules as a calculation key, or dynamically.

FIG. 12 shows an example of a timing chart of activation of localisationmodules as a function of a common activation signal.

As shown, a common activation signal, denoted sync, comprises hereperiodic pulses, of period P1 and duration P2. The purpose of each pulseof the sync signal, representing an activation “instruction”, is thesequential activation of the localisation modules (all or thosepreviously selected). P2 corresponds to the minimum durationguaranteeing the detection of the common signal by all the localisationmodules concerned.

Upon receipt of an activation “instruction” of the sync signal, eachlocalisation module calculates or determines the time delay value at theend of which it has to be activated, i.e., typically the instant atwhich the switch 715 commands the selective amplifier 720 to generate asine wave voltage at the terminals of the solenoid 730, allowing thelatter to generate a sufficient radiation power. The switch 715 is, forexample, according to this example, a microcontroller or a circuitcomprising two monostable trigger circuits (one being used as a counterand the other as a switch).

The activation of each localisation module i is shown in FIG. 12, by anActiv. Mi signal. Thus, for example, the localisation module 0 isactivated between instants t1+P2 and t1+P2+P3, P3 corresponding here tothe duration of activation of each localisation module (P3 is heredefined as P1=P2+n×P3, where n represents the number of localisationmodules to be activated during a period P1), as shown by the Activ. MOsignal. Similarly, the localisation module 1 is activated between timesT1+P2+P3 and t1+P2+2×P3, as represented by the Activ. M1 signal. Moregenerally, the localisation module i is activated between instantst+P2+i×P3 and t+P2+(i+1)×P3 where t represents the instant of receptionof an activation “instruction” from a common activation signal.

FIG. 13, comprising FIGS. 13 a and 13 b, shows the third example of analgorithm which can be used to sequentially activate a set oflocalisation modules by means of a common activation signal. FIG. 13 ashows certain steps implemented in the central processing system whileFIG. 13 b shows certain steps implemented in each localisation module.

As shown in FIG. 13 a, a first step (step 1300) consists here ofobtaining a value representing the present instant, for example usingthe GetTime( ) function, this value being stored in a time variable. Thecommon activation signal sync, or more precisely an activation“instruction”, is then emitted during the time interval P2 (step 1305)and the variable i, representing a localisation module index, isinitialized at zero (step 1310).

In a next step, the position (in two or in three dimensions) of anactivated localisation module is obtained (step 1315). This position canin particular be obtained as described above using a central processingunit (255, 255′, or 255″). The position obtained is associated with thelocalisation module i (step 1320) and the value of the variable i isincremented by one (step 1325).

A test is then performed to determine whether the value of the variablei is less than the number n of localisation modules the positions ofwhich are estimated during a period P1. If not, i.e. after havingobtained the position of each localisation module the positions of whichare estimated during a period P1, the algorithm returns to step 1300 tobegin a new cycle of obtaining positions.

If, on the other hand, the value of the variable i is less than thenumber n of localisation modules the positions of which are estimatedduring a period P1, the current instant is compared with the previouslystored instant (time) to which are added period P2 and, as necessary,period P3 multiplied by the value of the index i or time+P2+P3+I×P3(step 1335).

If the value representing the current instant is less than the valuetime+P2+P3+i×P3, the algorithm loops back to step 1335 (as thelocalisation module the position of which has been obtained is stillactivated, the position of another localisation module cannot beobtained). If, on the other hand, the value representing the currentinstant is not less than the value time+P2+i×P3, the algorithm returnsto step 1315 to obtain the position of the localisation module havingindex i (the value of which had previously been incremented).

In parallel with the steps described with reference to FIG. 13 a, eachlocalisation module the position of which has to be obtained executessteps such as those shown in FIG. 13 b.

After receiving an activation “instruction” (step 1340), typically apulse of the sync signal, a time delay value P(i), where i represents alocalisation module index (different for each localisation module andcomprised between zero and the number of localisation modules minusone), is calculated (step 1345) according to the following expression:

P(i)=P2+i×P3

P(i) thus represents a duration between the start of the activation“instruction” of the common activation signal and the start ofactivation of the localisation module having the index i.

A value representing the current instant is then obtained, for exampleusing the GetTime( ) function, and assigned to the variables t and timer(step 1350).

Next, the value of the timer variable is subtracted from that of thevariable t and the result is compared with the time delay value P(i)previously calculated (step 1355).

If the difference between the variables t and timer is not less than thetime delay value P(i), a value representing the current instant isobtained again and assigned to the variable t (step 1360) and thealgorithm returns to step 1355. On the other hand, if the differencebetween the variables t and timer is less than the time delay valueP(i), the localisation module having the index i is activated during atime interval P3 (step 1365) such that its position can be obtained.

While the order of activation of the localisation modules can bepredetermined and correspond to indices thereof (or a similar item ofdata), it is also possible to use a dynamic system of activation of thelocalisation modules as described below with reference to FIG. 14. Sucha system can, in particular, be based on a time-division multiple accessalgorithm (the technique of time-division multiple access is, inparticular, operated by second-generation mobile telephone networks suchas Global System for Mobile communications (GSM) and variants accordingto which the number of timeslots can be dynamically reserved exist instandards such as the Bluetooth standard, Bluetooth is a trademark).

Such an embodiment has the advantage of not requiring predefinedpositions in the sequence of activation of localisation modules.Moreover, such dynamic management makes it possible to resolve conflictsbetween localisation modules which have identical calculated orpredefined time delay values.

According to a particular embodiment, the duration between twoactivation “instructions” of the common activation signal is dividedinto a number n+1 of timeslots, of a fixed and predetermined duration,referenced TS0 to TSn. A common activation cycle thus contains n+1timeslots.

The first timeslot TS0 begins at the moment of emission of an activation“instruction” of the common activation signal. It is specific andreserved for the arrival of new localisation modules.

For the duration of timeslot TS0, the localisation modules not yethaving a timeslot assigned emit via their solenoid. If the centralprocessing system receives signals from the localisation modules duringthe period of timeslot TS0, the central processing system emits asecondary activation signal at the end of each unassigned timeslot. Thissecondary activation signal can, for example, be a specific tonemodulating an FM signal. The localisation modules are then informed ofall of the free timeslots.

Each localisation module performs a random selection to determine a freetimeslot during which it will emit during the next cycle.

At each cycle and for each free timeslot, there are the following threepossibilities:

-   -   the timeslot remains free: no localisation module has selected        it. The central processing system therefore continues to        indicate that the timeslot is free by emitting a secondary        activation signal at the end of the timeslot;    -   the timeslot has been selected by a single localisation module,        which emits during the period of the timeslot: the central        processing system then ceases to emit a secondary activation        signal at the end of this timeslot. The disappearance of the        secondary activation signal informs the localisation module that        its timeslot assignment is in effect, and    -   the timeslot has been selected by several localisation modules,        which emit during the period of the timeslot: the central        processing system detects a collision of signals and continues        to indicate that the timeslot is free by emitting a secondary        activation signal at the end of the timeslot.

Cases of collisions are resolved for example by algorithms such as thosementioned in the section entitled “Collision backoff and retransmission”in the IEEE 802.3 Ethernet standard.

The release of timeslots is managed by the detection of the absence ofemission by a localisation module. A time delay is then triggered. If,during the whole of the time delay, the central processing system doesnot receive an emission from a localisation module, the correspondingtimeslot is considered released.

The timing chart in FIG. 14 shows activation cycles of 25 ms for whichthe central processing system emits an activation “instruction” (in acommon activation signal) at the beginning of each cycle, each cyclebeing divided into five timeslots referenced TS0 to TS4.

The crosses on the timing chart indicate collisions duringallocalisations of timeslots to the localisation modules.

Hypothetically, during the first cycle of the timing chart, timeslot TS1is here already allocated to a localisation module which is emitting.

Steps E1 to E6 of the timing chart show the allocalisation of timeslotsto localisation modules which appear on the detection surface inquestion:

-   -   step E1: new localisation modules (with no allocated timeslot)        emit by default on timeslot TS0. In response, the central        processing system emits secondary activation signals at the end        of the free timeslots (here timeslots TS2, TS3 and TS4). The new        localisation modules perform random selections to assign        timeslots on the basis of the free timeslots. Two of them select        timeslot TS2, a third selects timeslot TS3;    -   step E2: there is a conflict on timeslot TS2. The central        processing system signals this by maintaining emission of the        secondary activation signal at the end of the timeslot,        indicating to the localisation modules awaiting assignment that        timeslot TS2 is still free. The localisation modules perform a        new random selection;    -   step E2 a: there is no conflict on timeslot TS3, the assignment        request is accepted. The central processing system signals this        by interrupting the emission of the secondary activation signal        at the end of timeslot TS3. This timeslot is now assigned;    -   step E3: no localisation module has selected timeslot TS2. The        central processing system signals that it is still available by        emitting a secondary activation signal at the end of timeslot        TS2;    -   step E4: there is a collision on timeslot TS4. The secondary        activation signal is maintained at the end of this timeslot to        indicate that it is not yet assigned;    -   step E5: two unassigned localisation modules have selected        timeslots TS2 and TS4. There is no conflict and the assignments        are accepted. The central processing system stops emitting        secondary activation signals at the end of these timeslots to        indicate they are allocated, and,    -   step E6: steady mode, each localisation module has been        allocated a timeslot.

Although, in the example described here, the final number oflocalisation modules is equal to the number of timeslots per activationcycle, the activation mechanisms do not impose such a constraint.

The common activation signal can be detected in each localisation moduleby a high-frequency receiver which demodulates the common activationsignal and transmits it to a microcontroller responsible for calculatingthe time delay associated with the localisation module. When the timedelay has elapsed, the localisation module emits a localisation signalby means of its solenoid by producing, for example, a square signal fora period P3 at the resonant frequency of the selective amplifierconnected to the solenoid.

Alternatively, the detection, in the high-frequency receiver of alocalisation module, of a switch of the common activation signal to aparticular state, for example a high state, can trigger a firstmonostable trigger circuit configured to produce a pulse after a timedelay period P(i) allocated to the localisation module. When the timedelay has elapsed, the falling edge of the first monostable triggercircuit initiates a second monostable trigger circuit which links thelocal oscillator to the selective amplifier connected to the solenoidfor a period P3. In this embodiment, the monostable trigger circuits canbe implemented using binary counters or circuits using the charging timeof an RC circuit. The local oscillator can be used as a clock signal ofthe binary counters.

The common activation signal can be a specific signal or an existingsignal. Thus, for example, it is possible to use the signal induced bythe synchronization frame of a screen used as a common activationsignal, making it possible to omit the high-frequency receiver in themobile element. In this case, the high-frequency receiver is replacedhere by an induction loop tuned to the refresh rate of the screen. Thisinduction loop constitutes a resonant RLC assembly on the frequencyspecific to the screen and connected to the input of the analog/digitalconverter of the microcontroller responsible for calculating the timedelay associated with the localisation module.

Similarly, the high-frequency receiver can be replaced by an inductionloop tuned to the frequency of the remote power supply for thelocalisation modules (emission of the frequency of the remote powersupply being interrupted cyclically in order to provide the commonactivation signal).

It should be noted here that the common activation signal, as a remotepower supply signal of the localisation modules, can be used to transferdata to localisation modules, for example by using frequency modulationencoding.

Similarly, the localisation signals emitted by the localisation modulescan be used by the localisation modules to address data, for example anidentifier of the localisation module in question and/or the status of aswitch, to the central processing system.

According to a particular embodiment, a microcontroller of a mobilelocalisation module generates a square signal of variable frequency.This frequency modulation makes it possible to encode a bit streamcorresponding to the data to be transferred, a frequency F1corresponding to a low state and a frequency F2 corresponding to a highstate. The frequencies F1 and F2 are preferably close to the frequencyof the selective amplifier of the localisation module such that theselective amplifier gain is high.

Still according to a particular embodiment, since the localisationmodules only emit during timeslots assigned to them, the centralprocessing system is able to identify from which localisation module thereceived data originate.

According to another particular embodiment, the local oscillator locatedin the mobile element generates a variable frequency signal. Thisfrequency modulation is implemented, for example, by means of anexternal polarisation induced by a change in impedance at the input ofthe local oscillator. Again, this frequency modulation makes it possibleto encode the bit stream corresponding to the data to be transferred.The modulated signal received by the central processing system can beprocessed by an analog input of this system in order to be converted andstored.

Alternatively, the signal received by the central processing system isdemodulated by an analog demodulation circuit in order to reconstructthe baseband signal. According to another alternative, the receivedsignal is amplified and sent to a clock input of an internal counterwhile a second internal counter acts as an internal time reference. Thissecond counter is triggered upon reception of the rising edge of theamplified signal and then is stopped when the first counter reaches apredefined value. The value obtained when the second counter stops isused to discriminate the frequencies of the modulated signal. The higherthe value to be reached by the first counter and the higher the clockfrequency of the second counter in relation to the frequencies of themodulated signal, the more the frequencies of the modulated signal canbe discriminated. Generally, the rate will be log₂ (number offrequencies discriminated) per activation cycle.

Data transfers to or from localisation modules can be encrypted in astandard manner, for example public and private keys of the RSA type.

The duration of activation of a localisation module can also becharacteristic of an item of data to be transmitted by the latter, inparticular its identity.

It is noted here that the use of a switch in the localisation modules tosupply the radiating elements (solenoids or similar) used to determinetheir position makes it possible to locate these modules in real timeand, consequently, to allow a large number of localisation modules to bemanaged. In fact, as shown in FIGS. 7 and 8, the excitation signal ofthe solenoid in the localisation modules is always available, thissignal being transmitted to the solenoid or not depending on theposition of the switch 715 (which can, in particular, incorporate amicrocontroller or monostable trigger circuits) and the switching timebeing negligible here.

By way of illustration, assuming that the cycle for obtaining positionsof localisation modules is 50 Hz and that 50 localisation modules areused, the activation time of each localisation module is about 0.4 ms.If the turn-on and stop time is of the order of 1% of the activationduration, this must be of the order of 40 μs.

According to a particular embodiment, the emission frequency of thesolenoid of the localisation modules is set within a range close to 100kHz. At this frequency, the electromagnetic coupling between thelocalisation module and the detection surface loops is mainly of amagnetic order.

This choice of frequency makes it possible to limit the interferenceinduced by a screen (positioned between the detection surface and thelocalisation modules) on the electromagnetic coupling between thelocalisation modules and the detection surface (the radiation from ascreen is mainly electrical in nature). It is therefore possible toplace the detection surface and the localisation modules to either sideof the screen while maintaining optimum operation of the system.

It is recalled that the strength of the magnetic field generated by asolenoid is given by the following formula:

$B = {c \cdot I \cdot \frac{N}{L}}$

wherein c is a constant, I is the intensity of the current passingthrough the solenoid, N is the number of turns of the solenoid, and L isthe length of the solenoid.

Since the dimensions of the solenoid are constrained so that thedimensions of the localisation module are reduced and allow forincorporation into usual objects and L is typically of the order of afew millimetres, N is then sized to obtain a sufficient magnetic fieldstrength.

Furthermore, in order to allow for correct coupling across the surfaceof a screen, the value of the current passing through the solenoid hasto be optimized. It is this which provides for the implementation of thelocal oscillator coupled to the radiating selective amplifier. The localoscillator generates the exact resonant frequency of the radiatingselective amplifier. When activated, the radiating selective amplifieroperates at its exact resonant frequency and ensures that the currentpassing through the solenoid is at a maximum.

Depending on the intended application, it may be necessary to limit theoperation of the system to a subset of available localisation modules orto associate a particular function with certain localisation modules.Thus, in an initialisation phase of the system, it may be necessary todefine a list of localisation modules the position of which need not becalculated (their electromagnetic emission is not activated by theactivation module). This list can vary over time and can differ from itsinitial value defined during the initialisation phase. It is alsopossible, in an initialisation phase, to assign a specific function orrole to a localisation module or a mobile element. Thus, for example, amobile element associated with a predefined localisation module can playthe role of a King if this mobile element is being used in a chessprogram, the same mobile element also being able to play the role of aneraser or felt-tip pen in a drawing application or even have the role ofa car in a driver training program.

By way of example, the association between localisation modules and afunction can be made by arranging the mobile elements comprising theselocalisation modules on specific parts of the detection surface andtriggering a recording. The control module for position detection andcapture then performs a complete activation sequence and the roles areassociated according to the respective positions of the mobile elements(e.g. pieces in a team A versus pieces in a team B).

When a screen is superimposed on the detection surface, it is possibleto choose a role in a contextual menu for each mobile element bydisplaying a menu near the position of each mobile element, offeringdifferent possible roles.

A particular application of the invention relates to board games whilemaking it possible to keep the convivial aspect of board games and thepleasure of handling real pieces or figures and benefiting from theinteractivity and dynamism of video games. In this field of application,a large touch screen is preferably superimposed on the surface for thedetection of the pieces.

The localisation modules are advantageously placed in the bases of thefigures used in the game, thus ensuring detection of the position of thefigures in the game.

The touch screen can display the game playing area on which the figureswill move, thus providing dynamic visual support. Typically, the screendisplays an animated and realistic environment for the figures(corridors in a spaceship for a science fiction game, geographical zonesfor a game of the “Risk” type, a chessboard if the figures are chesspieces, etc.).

When launching the game, the system offers to assign a function to themobile elements in order to enable the program to make a relationshipbetween the identifier of one or more detection modules and the figurerepresented by this mobile element. This can be done by displaying aspecific menu for selecting roles on the screen near the position ofeach figure placed on the board.

When pieces have been recorded, i.e. their roles have been assigned tothem, they become genuine interfaces in the game. The system can thencontinuously verify that the movements of the figures properly respectthe limitations on movement imposed by the rules of the game, takinginto account their role in the game (moving from square to square in acorridor for example, respecting the appropriate movements for a game ofchess, etc.). The system can also calculate and display on the screenthe lines of sight between two figures in a combat game or automaticallycalculate and display possible captures in chess. It is also possible totrigger contextual visual animations under a figure or from a figure.Thus, selecting a weapon shot on the menu for a figure can producespecific lighting around the shooter and display tracer shots betweentwo figures. Similarly, it is possible to trigger contextual audioanimations when the relative position of two figures permits. Forexample, if, when moving a figure, the system determines the existenceof a line of sight with another figure, an audio “target in sight” alarmcan be triggered by the system.

Similarly, it is possible to display contextual menus depending on theposition of the figures (a menu to calculate the result of hand-to-handcombat is displayed if two enemy figures are at a minimum distanceapart), offer automatic online help when a player makes a forbiddenmovement with his figure, and change the display on the screen whenplayers perform turns with the figures.

In addition, specific characteristics (colour, eraser or line thicknessfunction for a mobile element representing a pencil) can be associatedwith the different mobile elements. They can be transmitted by thelocalisation modules (directly or as a function of associated time delayvalues), as described above. The selection of a function or colour canbe displayed on the object comprising the localisation module inquestion by dedicated Light-Emitting Diode (LED) display, for example.

For the same mobile element, it is also possible to change itscharacteristics by modifying one of these parameters upon user action (aring, a thumbwheel, or a switch on the pen for example). On the basis ofthese mechanical interventions, a microcontroller present in thelocalisation module can modify the associated time delay value ortransmit data, in particular in the form of a bit stream, indicatingthat a new function has been selected.

Other particular applications of the invention relate to the control ofindependent objects such as cars, boats, helicopters, and aeroplanes.Thus, for example, for a motor race, the invention can provide drivingassistance for a car controlled by a player and control other vehiclesdriven by the system. If the vehicles are equipped with two localisationmodules, it is possible to smooth the calculated trajectories.

Similarly, for a helicopter piloting application, the invention canprovide help in piloting, in particular during takeoff and landingphases, while benefiting from simplification of the on-board electronicsin the helicopter (the gyroscope usually used becomes unnecessary forexample). If the airborne mobile object has three localisation modules,control can be achieved in three dimensions, since the centralprocessing system has six degrees of freedom in real time (x-axis,y-axis, altitude, pitch, roll and heading).

Naturally, in order to provide for specific requirements, a personskilled in the field of the invention can apply modifications to theabove description.

1. Method for interfacing in real time a plurality of mobile elements(110, 110′) with a computer system, the method being characterized inthat it comprises the following steps, transmission (1015, 1114, 1305)of an activation signal to at least one localisation module (700, 700-1,700-2) incorporated in at least one mobile element of said plurality ofmobile elements; sequential activation of said at least one localisationmodule, said activation comprising a switching step to excite aradiating element of said at least one localisation module; reception ofat least one signal from said at least one activated localisationmodule; calculation (1020, 1116), on the basis of said at least onereceived signal, of at least one item of information on the position ofsaid mobile element comprising said at least one activated localisationmodule, a single localisation module being able to be activated at agiven instant.
 2. Method according to claim 1 wherein said activationsignal comprises an item of data making it possible to identify alocalisation module in order to selectively activate a singlelocalisation module.
 3. Method according to claim 1 wherein saidactivation signal is a common activation signal for common control ofthe activation of a plurality of localisation modules.
 4. Methodaccording to claim 3 further comprising a step to calculate a time delayvalue for each localisation module of said plurality of localisationmodules, said time delay value representing a time interval between thereception of an activation signal and the activation of the localisationmodule.
 5. Method according to claim 4 wherein each time delay value isdetermined according to an item of localisation module identificationdata.
 6. Method according to claim 4 wherein each time delay value isdynamically determined.
 7. Method according to claim 6 wherein each timedelay value is determined according to a time-division multiple accessalgorithm.
 8. Method according to claim 3 wherein said common activationsignal is induced by a signal used independently of said method. 9.Method according to claim 1 further comprising a step to calculate atleast one item of information on the orientation of said mobile element,said mobile element comprising at least two localisation modules. 10.Method according to claim 1 further comprising a step of transmitting atleast one item of data from said at least one localisation module tosaid computer system.
 11. Method according to claim 1 further comprisinga step to check the validity (1010, 1112) of said at least onelocalisation module, said step of sequential activation of said at leastone localisation module being performed in response to said validitycheck step.
 12. Method according to claim 11 further comprising a stepof assigning (1138, 1140) a state of validity or invalidity to said atleast one localisation module, said state of validity or invaliditybeing determined according to said at least item of positioninformation.
 13. Method according to claim 1 wherein said step ofreception of at least one signal comprises a step of sequentialselection of a plurality of receivers, said at least one signal beingreceived by least one receiver selected from said plurality ofreceivers.
 14. Mobile element (100, 110′) for a device to interface aplurality of mobile elements with a computer system, said mobile elementbeing characterized in that it comprises at least one localisationmodule (700, 700-1, 700-2), said localisation module comprising thefollowing means, means (730) for emitting a signal for making itpossible to calculate the position of said localisation module; means(720, 725) for generating an excitation signal of said means foremitting a signal; switching means (715) for controlling thetransmission of said excitation signal to said means for emitting asignal; and, means (710) for receiving an activation signal and,according to at least one item of information of said activation signal,activating said switching means to enable the emission of a signal whichcan be used to calculate the position of said localisation module. 15.Mobile element according to claim 14, said means for receiving anactivation signal comprising means for calculating a time delay value,said time delay value representing a time interval between the receptionof an activation signal and the activation of said switching means. 16.Mobile element according to claim 14, said at least one localisationmodule comprising at least one solenoid, excitable by induction, forsupplying electric power to components of said at least one localisationmodule.
 17. Device for interfacing a plurality of mobile elements (110,110′) with a computer system, the device comprising means suitable forthe implementation of each of the steps of the method according toclaim
 1. 18. Mobile element according to claim 15, said at least onelocalisation module comprising at least one solenoid, excitable byinduction, for supplying electric power to components of said at leastone localisation module.